This invention relates to lighting systems and particularly to a lighting system designed to operate through a viewport and to provide illumination to the interior of hypobaric or hyperbaric chambers from a light source located outside the wall of the chamber. Hyperbaric research, diver recompression chambers, and the like require safe and effective means for internal illumination. A hyperbaric chamber is designed to withstand internal pressures greater than atmospheric. A hypobaric chamber is designed to withstand internal pressures less than atmospheric. Waterfilled hyperbaric chambers are frequently used for diver research and the like.
Several methods have been used for illuminating hypobaric and hyperbaric chambers. Incandescent lamps generally enclosed in protective enclosures have been commonly used for internally located light sources. These light sources have introduced electrical and fire hazards into the chambers. In addition, the heat generated by the light source was dissipated into the chamber, thus adding to the heat load in the system. All systems which use internally located light sources have required extra openings through the chamber wall to provide electrical power to the lights.
A wide variety of commercial incandescent lamps have been used with externally located light sources for introducing light to the interior of hyperbaric or hypobaric chambers through viewports. The most common problem has been the heating of the viewport by infrared radiation which accompanies the visible light. This can cause severe thermal stresses in the viewport material and has on occasion resulted in the cracking of the viewports; plastic viewports have sometimes been fused or charred on the surface. Such overheating and subsequent mechanical damage can lead to the catastrophic failure of the viewport and the loss of life and property. Attempts to prevent overheating of the viewports have included: the use of low power lamps which give off less heat and less light; the spacing of the light source at a greater distance from the viewport with subsequent reduction in both heating and lighting effect; and the use of infrared absorbing glass to extract the heat which requires the heat absorbed by the glass to in turn be dissipated by a heat sink or other method.
Additional problems occur in water-filled hyperbaric chambers (WET POTS) where light directed into the water-filled chamber directly illuminates minute particles of matter in the water, making it difficult for divers working within such a chamber or persons looking through viewports to see properly due to excessive reflection of light from the minute particles of matter.